January represents 12% of the Lincolnshire-based garden centre supplier's sales of wild-bird food, and the cold snap means high energy foods including peanuts and suet for small birds such as wrens may reach 40% of total annual sales over the winter period.
Gardman marketing manager Suzanne Broughton said: "High energy foods such as fat/suet products, sunflower seeds and peanuts are very important for wild birds when the weather is so cold. Clean, fresh water is also vital. Numbers of bird species such as goldfinches may fall in the winter as they emigrate but small species such as wrens are particularly vulnerable.
"Winter sales, which run from December until February, of wild bird food account for on average more than 30% of the year's total sales. Within these months high energy foods such as peanuts, fat snax and suet feats see a higher percentage share of sales, many reaching more than 40%."
Gardman believes sales uplift in August is driven by garden centres getting ready for the winter and stocking up on new feeds.
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